Ganes Creek Prospect, Iditarod District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: This prospect consists of a sulfide-bearing veins and veinlets with tourmaline, quartz, fluorite, and white mica; it occurs in a small quartz porphyry body that intrudes andesitic roof pendants that overlie the Beaver Mountains volcanic field (Bundtzen and Laird, 1982; Miller and Bundtzen, 1994). The quartz porphyry intrusion is probably a phase of the composite Beaver Mountains pluton that has been dated at 70.3 Ma. Szumigala (1993, 1996) who investigated this area for Battle Mountain characterizes the prospect as in the northern part of the 'south quartz zone'. The deposit is controlled by a near-vertical fracture set that strikes about N75-80E. The deposit is possibly part of a mineralized trend that extends from the Cirque prospect (ID009) northeast to the head of Ganes Creek, a distance of more than 1.8 miles. The mineralization consists of parallel quartz-white mica-tourmaline-sulfide veins, 1 to 7 inches thick within the tourmalinized, quartz-porphyry intrusion. A sulfide-bearing zone about 50 by 100 feet in size that was sampled by Anaconda Minerals Company contains abundant fluorite, axinite, and topaz (D.B. Obolewicz, written communication, 1981). Veins with quartz and white mica typically have a vuggy coxcomb texture whereas the tourmaline-axinite- rich zones are tight; this suggests the deposit was formed by several different hydrothermal fluids over a period of time. Samples collected by the U.S. Geological Survey and the Alaska Division of Geological and Geophysical Surveys contained up to 332 parts per million (ppm) silver, 8.00 percent copper, 100 ppm antimony, and 100 ppm tin (Bundtzen and Laird, 1982; Miller, Bundtzen, and Gray, 2005). Samples collected by Anaconda Minerals (D.B. Obolewicz, written communication, 1981) contained up to 3,400 ppm copper, more than 2.00 percent lead, 450 ppm zinc, more than 100 ppm silver, more than 2,000 ppm tungsten, 250 parts per billion (ppb) gold, more than 1,000 ppm arsenic, 425 ppm tin, and 330 ppm antimony. One grab sample collected by Battle Mountain Mining Company contained 52.4 ppm gold and 1.53 percent lead (Szumigala, 1993). The high lead values in grab samples can be attributed to visible galena in hand specimens. The high copper and silver values found in the grab samples might be attributed to tetrahedrite and jamesonite observed in hand specimens. Wolframite was also identified in hand specimens.
Workings: Personnel from the U.S. Geological Survey and Alaska Division of Geological and Geophysical Surveys sampled the deposit in 1981. In 1981, Anaconda Minerals examined the prospect (D. Obolewicz, written communication, 1981). Szumigala (1993, 1996) investigated the prospect in the late 1980s, while working for Battle Mountain Mining Company.
Age: Undated; may be related to emplacement of the Beaver Mountains stock which has been dated at 70.3 Ma (Bundtzen and Laird, 1982).
Alteration: Development of greisen with tourmaline, quartz, axinite, white mica, and topaz.
Commodities (Major) - Ag, Au, Cu; (Minor) - Pb, Sb, Sn, W, Zn
Development Status: None
Deposit Model: Sn-polymetallic veins (Cox and Singer, 1986; model 20b).
12 entries listed. 8 valid minerals.
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Bundtzen, T.K., and Laird, G.M., 1982, Geologic map of the Iditarod D-2 and eastern D-3 quadrangles, Alaska: Alaska Division of Geological and Geophysical Surveys Geologic Report 72, 1 sheet, scale 1:63,360. McGimsey, R.G., Miller, M.L., and Arbogast, B.F., 1988, Paper version of analytical results, and sample locality map for rock samples from the Iditarod quadrangle, Alaska: U.S. Geological Survey Open-File Report 88-421-A, 110 p., 1 sheet, scale 1:250,000. Miller, M.L., and Bundtzen, T.K., 1994, Generalized geologic map of the Iditarod quadrangle, Alaska showing potassium-argon, major oxide, trace element, fossil, paleocurrent, and archeological sample localities: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-A, 48 pages; 1 sheet, scale 1:250,000. Miller, M.L., Bundtzen, T.K., and Gray, J.E., 2005, Mineral resource assessment of the Iditarod quadrangle, west-central Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-B, scale 1:250,000, pamphlet. Szumigala, D.J., 1993, Gold mineralization related to Cretaceous-Tertiary magmatism in the Kuskokwim Mountains of west-central and southwestern Alaska: Los Angeles, University of California Ph.D. dissertation, 300 p. Szumigala, D.J., 1996, Gold mineralization related to Cretaceous-Tertiary magmatism in west-central Alaska-A geochemical model and prospecting guide for the Kuskokwim region: Geological Society of Nevada Symposium Proceedings, p. 1317-1340.